Attention has been focused upon MRAM that is known as the integrated magnetic memory having the packaging density equivalent to that of DRAM, the high speed equivalent to that of SRAM and the unlimited rewritable capability. In addition, the thin-film magnetic heads, magnetic sensors and the like utilizing the magnetoresistive devices such as GMR (giant magnetoresistive) device or TMR (tunneling magnetoresistive) device have been developed rapidly.
For example, there is a magnetoresistive device that has a bottom electrode formed on a silicon, glass or like substrate and an eight-layer film formed as the multilayer film on the bottom electrode for providing the magnetoresistive device, wherein the eight layers include the Ta layer as the lowest layer, the PtMn layer on the Ta layer and acting as the anti-ferromagnetic layer, the pinned layer, the barrier layer, free layer and the protective layer (hard mask), all of which are formed one on another in the order in which they are listed above.
As proposed and disclosed in Japanese patent application No. 2003-203313, Japanese patent application No. 2004-326831 and Japanese patent application 2005-42143, all of which are now opened for the public examination, the magnetoresistive device includes a substrate on which the multilayer magnetic film is formed, in which the substrate is processed by using the thin film processing techniques such as the reactive ion etching (RIE) process, the ion beam etching (IBE) process and the like so that the required performance can be provided.
The inventors of the current patent application have proposed the reactive ion etching process using alcohol (e.g. methanol) as the etching gas that contains at least one or more hydroxyl group. This can increase the etching speed, as compared with the conventional process using the carbon monoxide gas containing ammonia gas as an additive, and can also minimize damages that might be caused mostly by the oxidation that may result from the etching process (as disclosed in Japanese patent application No. 2005-42143).